Toilets using a vertically fed flexible tube to line the bowl have been described in UK patent specification GB 1,525,613 and GB 2,160,417. In these references the tube used to line the toilet bowl is stored as a folded ring around the outside of the toilet bowl which is sequentially unfolded as the tube is pulled over the rim and down inside the bowl. The tube is pinched or sealed closed at the bottom of the bowl to contain the waste and also to prevent odors escaping from the previously used lower portion of the tube that has been deposited beneath the bowl.
This method of lining a toilet with a vertical tube has disadvantages which have limited the commercial exploitation of toilets employing this principle. An excess of tube material is required for each flush which makes the toilet expensive to operate. To be folded and stored outside the bowl, the tube diameter has to be much larger than the effective inside diameter of the bow. This surplus of material makes large folds which project within the bowl thus reducing the bowl volume and causing the soiling of surfaces much closer to the seat than one expects from a conventional toilet. Furthermore, whereas a very thin material would be adequate to protect bowl surfaces, the tube material has to be relatively thicker to contain the waste in an odor free manner and to prevent leakage while it is stored below the toilet. The combination of excess thickness and excess diameter limits the amount of tube material that can be stored in the small space around the toilet bowl thus requiring the toilet to be restocked at more frequent intervals than would normally be desired. Also, the storage of tube material around the toilet results in having to locate the bowl and the seat further back from the front of the toilet enclosure making it uncomfortable for short people and children to sit on.
Another disadvantage of the vertical tube toilet is that the total height required for the bowl, the feeding and sealing mechanism beneath the bowl and the storage space below that is greater than the height of a conventional toilet and, therefore, in practice toilets of this type often project below the floor which prohibits their use as portable appliances and makes removal of the waste more difficult.
A type of dry toilet which uses a disposable sheet to receive and remove the toilet waste and which avoids the disadvantages of the tubular bag toilet such as the excessive vertical height and the limited space for liner supply has been described by HARM in U.S. Pat. No. 2,205,405 with subsequent improvements described in U.S. Pat. No. 2,983,090. This toilet uses a continuous rectangular sheet supplied from a roll positioned horizontally below the toilet bowl. The flat sheet is pulled from the roll and over the upper lip of the toilet bowl and then through the bowl space. As the sheet progresses across the bowl space the opposed edges of the sheet are brought together and joined between a pair of rollers that grip the edges of the sheet and also serve to pull the sheet through the bowl space. This action folds the flat sheet in half and results in the formation of a wedge shaped container within the bowl space. The dimensional restraints that are necessary to form this type of wedge shaped container results in a toilet bowl space which is unusually shallow and overly wide at one end and very narrow at the other end. These restrictions on depth and width can be unpleasant to persons use to conventional toilets. To increase the effective depth of the bowl space to an acceptable level the toilet rim above the bowl space is shown to be unusually high and this will result in soiling the rim which is not protected by the liner sheet. This is particularly so at the narrow end where the width of the bowl space is less than the width of the opening in the toilet seat.
The wedge shaped container and its associated mechanism results in an awkwardly dimensioned enclosure for installation and use in conventional toilet rooms. As can be seen in U.S. Pat. No. 2,205,405 if the toilet is installed parallel to a wall it would be necessary for the user to sit at a 45 degree angle. In U.S. Pat. No. 2,983,090 this has been corrected but to make room for the drive mechanism much greater distance is required from the back wall than is desirable, particulary in public transport applications where toilet space is very limited. This configuration also requires the seat of the toilet to be set back from the edge of a bench type enclosure. For extra comfort and cleanliness it is desirable that the bowl and seat protrude forward from the enclosure and this is not possible with this type of toilet mechanism.
Another disadvantage of this type of toilet is the inherent difficulty of installing a new roll of liner sheet or replacing a torn liner sheet. In both situations it is necessary to disassemble the toilet enclosure and manually thread the liner sheet from the roll and through the guides and into the pulling mechanism, a process requiring the skill of a trained person and sufficient extra room space for the disassembly process.